1. Field of the Invention
The present invention relates to infrared communication repeater apparatus and method in data communications systems for performing communications of the direct emission type while causing out-going infrared radiation to have directivity in infrared communications.
2. Description of the Prior Art
Data communication methods using infrared radiation may typically include two approaches which follow.
A first method is a direct emission type communication method for performing transmission and reception of infrared signal light with one infrared transmitter (simply referred to as “transmitter” hereinafter) and its associated infrared receiver (“receiver”).
A second method is a diffusion type communication method of causing infrared radiation as emitted from transmitters to reflect off from ceilings, walls or the like and then allowing receivers to receive the resultant reflected and scattered rays of infrared signal light.
The diffusion type communication method is superior in flexibility of layout of transmitters and receivers than the direct emission type communication method due to the use of reflection and diffusion of infrared signal light at the ceiling or the like; however, the former method is more significant in required transmitter output than the latter because of a reduction or attenuation of the intensity of light in reflection and diffusion events, and also remains higher in reception sensitivity as required for receivers concerned.
A further problem faced with the diffusion type communication method is that the arrival time of infrared radiation signal light at an intended receiver side tends to be retarded or delayed upon affection of multi-paths originated from optical reflection and diffusion, which in turn leads to the risk of interference between a presently received infrared radiation signal and its succeeding one, resulting in limitations of data transmission rate.
On the other hand, the direct emission type communication method is featured in that while any obstructions should not be present between associative communication devices with complete line-of-sight “transparency” or visibility being required therebetween, high-speed data transmission is attainable as compared to the diffusion type communication method because of the fact that any multipath affection leading to occurrence of a delay in reception of infrared signal light hardly takes place unlike the diffusion type communication method, which in turn causes the output required for transmitters to be less than that in the diffusion type communication method while reducing the reception sensitivity as required for transmitters.
In the prior known direct emission type communications apparatus including infrared communication equipment for performing infrared communications by use of standard protocols of IrDA (Infrared Data Association) with regard to infrared communication methods, one-to-one (1-to-1) type communications schemes are employed in most applications, which renders N-to-N type simultaneous communicability unattainable although 1-to-N type communications forms are possible.